Flattening Waterstones

Been doing a little preparation for a video on sharpening (or part of a series on sharpening to be exact).

One of the popular sharpening methods is using Japanese waterstones, sometimes using a jig such as the Veritas MkII covered recently.

I like to think of sharpness of an edge as the interaction of two smooth planes. The smoother the planes, the sharper the edge. However, you can’t get a smooth plane if your sharpening surface isn’t smooth. In the case of waterstones, this means they need to be flat.

You need to keep on top of this – it is very easy to get dishing in your stone (a patch of increased wear), so a regular flattening (before and after each job would be good practice, and therefore would take little time).

To flatten a waterstone, you can (apparently) rub two together, flattening both, but to my mind this would only really be effective if both stones were the same grade. These are not particularly cheap, so I only have one of each! The stones I have are 1000 grit and 6000 grit. That does not correlate to sandpaper if you were wondering – I will do a separate post about that shortly.

Instead, I prefer to use a known flat surface (in this case 10mm plate glass), and affix some 180 sandpaper to it to flatten the stones. It is prety easy from there – keep rubbing until the stone has a uniform surface. As you can see in the next series of images, I went a bit overboard when first using the stones a few years ago when I got them, and went way too long without reflattening them, which caused significant dishing. I have been using the other side from then on, but for this article, decided to return to the dished side, and get it flat once again.

The first photo is after quite a lot of sanding, and still the hollow is very apparent. The second photo was with the end in sight – the dishing is almost gone. The final photo shows (finally) a nice uniform surface which means the stone is flat once again.